This project is concerned with the identification and quantitative description of the contributions of the principal afferent projection systems, (a) to the functional properties of the individual neurons comprising somatic sensory areas I and II of the primate cerebral cortex and (b) to the fine structure of the body representation found within these regions. More specifically, these studies employ the techniques of single unit analysis and surgical ablation to determine if the multiple somatic afferent systems contribute differentially (a) to the details of the cortical representation of the body, and (b) to the representation of stimulus features in the electrical activity of individual cortical neurons. The data are expected to bear upon the hypothesis that the distortions of somatic sensibility commonly associated with certain neurological disorders result from defective interactions among those multiple somatic afferent projection systems which are convergent at thalamo-cortical levels of the central nervous system.